Catalysts for polymerizing alpha-olefins and process for polymerizing alpha-olefins in contact with said catalysts

ABSTRACT

New highly active and highly stereospecific catalysts for the polymerization of alpha-olefins are disclosed, the starting components of which are 
     (a) an organometallic-compound of Al free from halogen atoms bound directly to the Al atom; 
     (b) an electron-donor compound (such as a Lewis base) in an amount such that 15% to 100% of the organometallic Al compound (a) is combined with the electron-donor compound; and 
     (c) a solid component comprising, at least on the surface, the reaction product of a halogenated Mg compound with a tetravalent Ti compound and with an electron-donor compound, the molar ratio electron-donor compound/Ti being higher than 0.2, and the molar ratio halogen atoms/Ti being higher than 4. 
     Processes for polymerizing the alpha-olefins and mixtures thereof with ethylene in contact with the new catalysts are also disclosed.

This is a continuation of application Ser. No. 832,473, filed Sept. 12,1977 (now abandoned) and which was, in its turn a continuation ofapplication Ser. No. 723,431, filed Sept. 14, 1976 (now abandoned).

THE PRIOR ART

Catalysts which are both highly active and highly stereospecific in thepolymerization of alpha-olefins, particularly propylEne, under givenconditions, are described in British Pat. No. 1,387,890.

The catalysts described in Br. No. 1,387,890 are generally prepared bystarting with a trialkyl Al compound partially complexed with anelectron-donor compound and the product obtained by finely grinding amixture of a Mg dihalide, an electron-donor compound, and a halogenatedTi compound.

The activity of the catalysts of the British patent, in thepolymerization of propylene and expressed in terms of gm polymer/gm Ti,is sufficiently high for commercial practice when the polymerization iscarried out in a liquid phase but in the absence of inert hydrocarbondiluents.

However, when the polymerization is carried out in an inert hydrocarbonsolvent (diluent), the activity of said catalysts decreases tounsatisfactory values, so far as concerns the possibility of obtaining apolymer useful as such and not requiring special purifyingafter-treatments for the removal of catalyst residues. Moreover, theisotacticity index of the polymers obtained with the aid of thecatalysts of the British patent is markedly reduced when thepolymerization is carried out in the presence of hydrogen as modifier orregulator of the molecular weight of the polymer produced.

Other catalysts are prepared starting with an alkyl Al compound and theproduct obtained by reacting a liquid Ti compound with a compositionprepared by finely grinding a mixture of a Mg dihalide, an organicester, and an organic Si compound.

Those last-mentioned catalysts exhibit high stereospecificity in thepolymerization of the alpha-olefins and in particular of propylene whenthe polymerization is carried out in the absence of hydrogen, but thestereospecificity is markedly decreased when hydrogen is used asmodifier or regulator of the molecular weight of the polymer produced.

If it is attempted to improve the stereospecificity of the lastmentioned catalysts in the presence of hydrogen by adding anelectron-donor compound to the alkyl Al compound, an improvement of theisotacticity index of the polymer is obtained but the activity of thecatalyst is consideraly reduced.

Polymerization catalysts have been obtained from an alkyl Al compound(triethyl Al) and from a catalyst component prepared by grindingmixtures of MgCl₂ with an organic ester and then reacting the groundproduct with TiCl₄.

The last mentioned catalysts exhibit both high activity and highstereospecificity in the polymerization of propylene, provided thepolymerization is carried out in the absence of hydrogen as modifier ofthe molecular weight of the polymer as it is produced. In contrast, whenhydrogen is present, the isotacticity index of the polymer is stronglyreduced.

THE PRESENT INVENTION

An object of this invention is to provide new catalysts which exhibitboth high activity and high stereospecificity in the polymerization ofalpha-olefins, in particular of propylene, or of mixtures thereof withethylene, to crystalline homopolymers or copolymers, even when hydrogenis present during the polymerization reaction as molecular weightmodifier or regulator, and even when the polymerization is carried outin an inert hydrocarbon solvent as the polymerization medium or diluent.

The new catalysts which insure the attainment of the aforesaidobject--and other objects--of the invention are prepared from thefollowing starting components:

(a) an organometallic Al compound free from halogen atoms bound directlyto the Al atom;

(b) an electron-donor compound (or a Lewis Base) used in an amount suchthat 15% to 100% of the organometallic Al compound (a) is combined withthe electron donor compound; and

(c) a solid component comprising, at least on the surface, the reactionproduct of a halogenated Mg compound with a tetravalent Ti compound andwith an electron-donor compound, the electron-donor/Ti compound molarratio being higher than 0.2, the halogen atoms/Ti molar ratio beinghigher than 4, and said reaction product being further characterized inthat at least 80% by weight of the tetravalent Ti compound containedtherein is insoluble in boiling n-heptane and at least 50% by weight ofthe Ti compound which is insoluble in boiling n-heptane is alsoinsoluble in Ti tetrachloride at 80° C., and still further characterizedin that the surface area of both the product insoluble in Titetrachloride at 80° C., and the surface area of component (c) as suchis higher than 20 m² /g, and preferably higher than 40 m² /g.

The new catalysts are preferably prepared by contacting component (c)with the product obtained by premixing components (a) and (b) for aperiod of time generally shorter than one hour.

High-performance catalysts, as to both activity and stereospecificitycan be obtained, also, by mixing together all of components (a), (b) and(c), or by first contacting component (c) with component (a) and thencontacting the resulting product with component (b), and vice versa.

In a presently preferred embodiment, the amount of electron-donorcompound (b) is such that from 20% to 40% of the organometallic Alcompound (a) is combined with the electron-donor compound.

Any electron-donor compound (or Lewis base) capable of forming a complexwith the organometallic Al compound (a), or of entering into asubstitution reaction with the organometallic Al compound (such as, forexample, in the following equation: ##STR1## may be used as component(b).

Examples of electron-donor compounds which are useful as component (b)include: amines, amides, ethers, ketones, nitriles, phosphines,stibines, arsines, phosphoramides, thioethers, thioesters, aldehydes,alcoholates, amides and salts of organic acids and of metals belongingto Groups I to IV of the Mendelyeev Periodic Table. If Al salts are usedas component (b), they can be formed in situ by reaction of an organicacid with the organometallic Al compound used as component (a).

Examples of specific electron-donor compounds useful as component (b)are: triethylamine, N,N'-dimethylpiperazine, diethylether,di-n.butylether, tetrahydrofuran, acetone, acetophenone, benzonitrile,tetramethylurea, nitrobenzene, Li-butylate, dimethylaminophenyl-lithiumand Na-dimethylamide.

Very good results, as regards both activity and stereospecificity of thecatalysts, have been achieved with the esters of the organic andinorganic oxygen-containing acids and with ethers like di-n.butylether.Particularly useful esters are, for example, the alkyl esters ofaromatic acids, such as benzoic p-methoxy or ethoxybenzoic and p-toluicacids, such as, for instance, ethyl benzoate, ethyl p-methoxybenzoate,methyl p-toluate and ethyl p-butoxybenzoate.

Additional examples of useful esters are: diethyl carbonate,triethylborate, ethyl pivalate, ethyl naphthoate, ethylo-chlorobenzoate, ethyl acetate, dimethyl maleate, alkyl or arylsilicates and methylmethacrylate.

The organometallic Al compounds useful as component (a) preferablyconsist of Al-trialkyl compounds, such as, for example, Al-triethyl,Al-tripropyl, Al-triisobutyl, or the compounds ##STR2## and Al(C₁₂H₂₅)₃.

Organometallic Al compounds containing two or more Al atoms boundthrough O or N atoms can also be used as component (a). Said compoundsare generally obtained by reacting an Al-trialkyl compound with water,with ammonia, or with a primary amine according to known methods.Examples of such compounds are: (C₂ H₅)₂ Al-O-Al(C₂ H₅)₂ ; ##STR3##

Still other Al compounds suitable for use as component (a) are, forexample, the hydrides of aluminum dialkyls, the alkoxides ofaluminum-dialkyls such as: Al(C₂ H₅)₂ (OC₂ H₅) and Al(C₄ H₉)₂ (OC₄ H₉),and the sesquialkoxides of Al-alkyls, such assesquiethoxy-aluminum-ethyl and sesquibutoxy-aluminum-butyl.

The electron-donor compound present in combined form in component (c)may be the same compound used as component (b) or may be a differentelectron-donor compound. Any electron-donor compound capable of formingcomplexes with the Mg halides may be used to prepare component (c).

Esters, ethers and diamines are preferably used. Examples of esters arethose already specified as useful as component (b) of the catalyst. Aparticularly efficacious diamine isN,N,N',N'-tetramethylethylenediamine.

Component (c) of the present invention preferably comprises, at least onthe surface, reaction products of halogenated Mg compounds selected fromMg dichloride and Mg dibromide, and halogenated compounds of tetravalentTi, in particular TiCl₄, TiBr₄ and Ti halogen-alcoholates, and complexesthereof with electron-donor compounds selected from amongst the organicesters, in particular from amongst the esters of the aromatic acids suchas, for example, benzoic acid. The nature and composition of component(c) of the present catalysts is further defined by the followingparameters:

(1) the Mg/Ti ratio is comprised between 3 and 40, preferably between 10and 30; the halogen atoms/Ti ratio is comprised between 10 and 90,preferably between 20 and 80, and the ratio moles of electron-donorcompound/Ti is higher than 0.2 and in particular is comprised between0.4 and 3 and more preferably between 1.2 and 3;

(2) at least 80% by weight and preferably 90% by weight, of the Ticompound contained in component (c) is insoluble in boiling n-heptane,while more than 50% by weight, in particular more than 70% by weight, ofthe Ti compounds insoluble in boiling heptane is insoluble in Titetrachloride at 80° C.;

(3) the surface area of component (c) as well as the area of the productinsoluble in Ti tetrachloride at 80° C. is generally larger than 100 m²/g and ranges in particular from 100 to 200 m² /g.

Components (c) particularly suitable for preparing very active catalystsaccording to this invention and having, contemporaneously, a highstereospecificity, are furthermore characterized in that in the X-raysspectrum thereof, the most intense line appearing in the spectrum of Mgdichloride and Mg dibromide of the normal type, as defined by standardsASTM 3-0854 and 15-836 for the chloride and bromide, respectively,exhibits a reduced relative intensity and appears asymmetricallybroadened, thus forming a halo showing an intensity peak shifted withrespect to interplanar distance d of the maximum intensity line, or thespectrum is characterized in that said maximum intensity line is nolonger present and in its place a halo appears having an intensity peakshifted with respect to distance d of said line. When MgCl₂ is used inpreparing component (c), the halo intensity peak is comprised betweend=2.44 A and 2.97 A.

Generally, the composition of component (c) may be expressed asconsisting for 70-80% by weight of Mg dichloride or Mg dibromide, thedifference to 100% consisting of the Ti compound and of theelectron-donor compound.

Component (c), however, may include, besides the abovecited components,also inert solid fillers in amounts that can reach 80% and above withrespect to the weight of component (c). Examples of such materials are:LiCl, CaCO₃, CaCl₂, Na₂ SO₄, Na₂ CO₃, Na₂ B₄ O₇, CaSO₄, AlCl₃, B₂ O₃,Al₂ O₃, SiO₂, TiO₂ etc.

We have observed that if component (c) is prepared in the presence ofthe inert solid matters, the surface area generally decreases. Moreparticularly, we have observed that when component (c) is homogeneouslymixed with agglomerating substances, in particular B₂ O₃, AlCl₃, etc.,the product obtained has a surface area generally below 10-20 m² /g.However, the performance of the catalysts obtained from such components(c) is still acceptable especially as regards the polymer yield.

In preparing component (c), it is possible to support the activeconstituents on inert carriers such as, for example, SiO₂ and Al₂ O₃having a high porosity. In this case, the Ti and Mg halogenatedcompounds and the electron-donor compound make up a reduced proportionwith respect to the total amount, thus permitting to obtain catalysts inwhich the amount of undesired matters, such as halogens, is minimal.

While the Mg/Ti ratio is generally higher than 1, it is lower than 1when TiO₂ and similar inert Ti compounds, such as the Ti salts ofoxygen-containing inorganic acids, are used as inert fillers.

Component (c) may be prepared by various methods.

A general method consists in starting from a particular composition orcarrier comprising a Mg halide and a complex between said Mg halide andan electron-donor compound in which the ratio Mg/moles of electron-donorcompound is higher than 2 and preferably ranges from 2 to 15, and intreating said composition or carrier with a liquid tetravalent Ticompound under conditions such that a certain amount of Ti compounds isfixed on the carrier, and in subsequently separating the solid reactionproduct from the liquid phase under conditions such that practically noTi compounds soluble in boiling n-heptane and extractable with Titetrachloride at 80° C. remain on the product.

The peculiar feature of the carrier to be treated with the liquid Ticompound is that of providing an X-rays spectrum in which thediffraction line of maximum intensity appearing in the spectrum of thecorresponding Mg halide of normal type exhibits a decreased relativeintensity and appears asymmetrically broadened so as to form a halo inwhich the intensity peak is shifted with respect to the maximumintensity line, or the maximum intensity line is not present in thespectrum and instead of it a halo appears having an intensity peakshifted with respect to distance d of the maximum intensity line.

This carrier, that is the starting product for the preparation ofcomponent (c) of the catalysts of this invention, can be obtained invarious ways.

A preferred method consists in grinding mixtures of a Mg halide, inparticular Mg dichloride or Mg dibromide, with an electron-donorcompound, optionally operating in the presence of a Ti compound and/orof an inert co-carrier and/or of agents which facilitate the grinding,such as silicone oils, until the above-described halos having theintensity peak shifted with respect to the maximum intensity line appearin the X-rays spectrum of the ground product.

The ground product is treated with a liquid halogenated Ti compound, inparticular TiCl₄, at such temperature (generally between roomtemperature and 200° C.) and for such time-period as to fix the properamount of Ti compound.

The solid product of the reaction is then separated from the liquidphase, for example by means of filtration, sedimentation, etc., undersuch conditions of temperature and/or dilution with the liquid Ticompound, that in the solid product, after extraction first with boilingn-heptane and then with TiCl₄ at 80° C., amounts of extractable Ticompounds exceeding 20% and 50% by weight respectively are no longerpresent.

One such method involves reacting, in an inert hydrocarbon solvent, ananhydrous Mg halide with an organic compound containing active hydrogenin the presence of an organic ester and in successively treating thereaction product with an organometallic Al compound.

In another such method, the order of the reactions is inverted, i.e.,the complex between the Mg halide and the active hydrogen-containingcompound is treated with the organometallic Al compound and theresulting product is then reacted with the organic ester.

The product obtained by said methods is washed with an inert hydrocarbonsolvent to remove any traces of free organometallic compound, and isthen reacted with a liquid Ti compound, in particular TiCl₄ at atemperature ranging from 20° to 200° C.

In accordance with this invention, the solid reaction product isseparated from the liquid phase under such filtration or sedimentationconditions that no, or practically no, Ti compounds extractable withboiling n-heptane and with Ti tetrachloride at 80° C. remain on thesolid component.

Again, and in accordance with this invention, the reaction product isseparated from the liquid phase under such conditions that no, orpractically no Ti compounds soluble in boiling heptane and in Titetrachloride at 80° C. remain on the solid product.

In the various methods of preparing the carrier, when a Mg halide isused it is preferably as anhydrous as possible (H₂ O content lower than1% by weight), especially when the catalyst component (c) of the presentcatalysts is prepared by grinding.

It is possible, however, to employ a hydrated Mg halide containinggenerally from 0.1 to 6 moles of H₂ O per mole of halide. Furthermore,it is possible to use oxygen-containing Mg compounds such as MgO,Mg(OH)₂, Mg(OH)Cl, Mg carbonate, Mg salts of organic acids, Mg silicate,Mg aluminates, Mg alcoholates and halogenated derivatives thereof. Inthese cases, the oxygen-containing Mg compound or the hydrated compoundis reacted with Ti-tetrachloride in excess, operating preferably at thetetrachloride boiling point and then hot-separating the solid product,preferably at the TiCl₄ boiling point.

The resulting solid product is treated in suspension in an inerthydrocarbon with an organic ester, in particular with an ester of anaromatic carboxylic acid in amounts equal to 1-20 moles per g-atom of Ticontained in the carrier, operating at temperatures ranging from roomtemperature to 200° C.

The solid product so treated is accurately separated from the unreactedester, and then reacted with a liquid halogenated Ti compound andseparated from the reaction liquid phase under the conditions specifiedfor the other methods of preparing the carrier described herein.

In all these preparation methods it is of essential importance that atleast 80% by weight of the Ti compounds contained in component (c) isinsoluble in boiling n-heptane, and that less than 50% of the Ticompounds insoluble in boiling heptane is extractable with Titetrachloride at 80° C. In fact, the presence of soluble Ti compounds isdetrimental to both the activity and the stereospecificity of thecatalyst, particularly when the polymerization is conducted in thepresence of hydrogen.

The new catalysts according to the present invention are preferablyemployed in the polymerization of alpha-olefins having at least threecarbon atoms and in particular in the preparation of crystallinepolymers and copolymers of propylene. They can be used, also, in thepolymerization of ethylene, in which case component (b) may be omitted.

The polymerization is conducted according to conventional methods,operating in a liquid phase, either in the presence or in the absence ofan inert hydrocarbon diluent, such as hexane, heptane, cyclohexane,etc., or in a gas phase.

The polymerization is generally carried out at a temperature comprisedbetween 0° and 150° C., preferably between 40° and 90° C., and atatmospheric pressure or at a higher pressure.

When crystalline copolymers of propylene are desired, it is preferableto polymerize propylene alone until a homopolymer equal to 60-90% of thetotal polymerizate is obtained, and to follow the propylenehomopolymerization step with one or more polymerization steps in whichmixtures of propylene and ethylene are polymerized or in which ethylenealone is polymerized, to obtain polymerizates containing from 5% to 30%by weight of polymerized ethylene, calculated on the weight of the totalpolymerizate. Mixtures of propylene and ethylene can be polymerized toobtain a copolymer containing, at most, 5% by weight of polymerizedethylene.

The following examples are given to illustrate the invention in moredetail, and are not intended to be limiting.

EXAMPLES 1 to 11 AND COMPARATIVE EXAMPLES 1-2 (A) Grinding

Anhydrous MgCl₂ (containing less than 1% by weight of water), ethylbenzoate (EB) and, optionally, a silicone were co-ground in twovibrating mills of the type VIBRATOM manufactured by N. V. TEMA'S,Gravenhage (Holland), having a total volume of one and six liters,respectively, and containing, respectively 3 and 18 kg of stainlesssteel balls of 16 mm diameter.

Grinding was effected employing a filling coefficient equal to 135 g/lof total volume (vacuum), at an interior temperature of the mill around40° C. and with grinding times, different from run to run, varying from50 to 100 hours.

Charging of the mill with the materials to be ground, the grinding, anddischarging of the product of the cogrinding from the mill occurred in anitrogen atmosphere.

In Example 10, the grinding was conducted in a rotary mill having acapacity of 1 liter, containing 120 stainless steel balls of 15.8 mmdiameter and rotated at 50 r.p.m.

Table 1 shows, for the various runs, the data relating to type andamount of the materials co-ground, the grinding conditions and thecharacteristics of the products obtained.

(B) Treatment with TiCl₄

A portion (15-50 g) of the co-ground product was transferred, always ina nitrogen atmosphere, into a 500 cc reactor, wherein it was contactedwith an excess of TiCl₄. The treatment with TiCl₄ took place attemperatures ranging from 80° to 135° C. for a 2-hour period, whereuponthe TiCl₄ in excess and the products soluble therein were removed byfiltration at the temperatures specified in Table 1. Two or morewashings with boiling hexane followed.

The resulting solid product was dried in a nitrogen atmosphere and aportion thereof was analyzed to determine the percent content of Ti andCl.

The data relating to the operating conditions employed in the variousruns during the treatment with TiCl₄ as well as the characteristics ofthe solid products thus obtained are reported in Table 1.

The stereospecificity and activity of these solid products (catalystcomponents) were determined in runs on the polymerization of propylenein a hydrocarbon solvent or in liquid monomer using, as co-catalysts,aluminum-trialkyls treated with electron-donor compounds.

(C) Polymerization in a Solvent

A 2500 cc autoclave, equipped with a stirrer and previously purifiedwith nitrogen at 60° C. was used. Polymerization was conducted at 60°C., at a propylene (C₃ ⁻) pressure of 5, 8 or 9 eff. atmosph. (keptconstant by addition of propylene during the polymerization runs) for a4 or 5 hour time-period.

As hydrocarbon solvent use was made of technical dearomatized andanhydrified (1000 cc) n-heptane (nC₇ ⁺), hexane (C₆ ⁺) or heptane (C₇⁺). Al(C₂ H₅)₃ [TEA] or Al(iC₄ H₉)₃ [TIBAL] was used as the Al trialkyl[component (a)], p-ethylanisate [PEA] or ethyl p-toluate [EPT] was usedas electron-donor compound. The Al trialkyl and electron-donor molarratio was comprised between 2.74 and 3.14. Hydrogen was present asmolecular weight modifier.

The autoclave was charged, in the order stated and in a propyleneatmosphere, with the solvent (870 cc), a portion of Al-alkyl and ofdonor previously mixed for 10' in 150 cc of the solvent, andcontemporaneously with the supported catalyst component in suspension in80 cc of solvent containing the remaining portion of Al-alkyl and ofdonor. Hydrogen and propylene were then introduced into the autoclaveuntil the polymerization pressure was reached, and the temperature wasraised to the value required.

At the conclusion of the polymerization run the solvent was removed bystripping with steam and the polymer so obtained was dried in a nitrogenatmosphere at 70° C.

(D) Polymerization In Liquid Monomer

Autoclaves of 30 liters and 135 liters capacity and equipped with astirrer were used. The polymerization temperature was 65° C., withpropylene at 26.5 eff. atmosph., for a time of 5 hours. Hydrogen (15 Nland 50 Nl) was present as molecular weight modifier.

Al(C₂ H₅)₃ in an amount of 12.5 g (runs in the 30-1, autoclave) andAl(iC₄ H₉)₃ in an amount of 36 g (runs in the 135 l autoclave), bothtreated with electron-donor compounds (p-methylanisate or ethylp-toluate in molar ratios of from 2.2 to 2.74) were employed as aluminumtrialkyls.

The autoclave was charged in the order stated and in a propyleneatmosphere, with the Al trialkyl in a 12% by weight heptane solution,with liquid propylene and with the donor.

The autoclave was heated to the polymerization temperature and thecatalyst component (c) and the hydrogen were then introduced.

At the conclusion of the polymerization, the residual propylene wasevaporated and the polymer was then dried in a nitrogen atmosphere at70° C.

In both runs (polymerization in a solvent and in liquid monomer), thedry polymer was weighed to calculate the yield with respect to titaniumpresent in the catalyst; moreover, the polymer was extracted withboiling n-heptane to determine the amount, in percent, of polymerinsoluble in boiling n-heptane.

Apparent density and inherent viscosity (in tetralin at 135° C.) of thepolymer thus obtained were determined. Table 2 reports the data relatingto the various polymerization runs and to the characteristics of thepolymers obtained.

                  TABLE 1                                                         ______________________________________                                        PREPARATION OF THE SUPPORTED                                                  CATALYST COMPONENT                                                                        Measure                                                                              EXAMPLES                                                                 Units    1        2     3                                       ______________________________________                                        GRINDING                                                                      Vibrating mill volume                                                                       1        6        6     6                                       Rotary mill volume                                                                          1                                                               MgCl.sub.2    g        530      651.5 651.5                                   EB amount     g        280      158.5 158.5                                   MgCl.sub.2 /EB molar ratio                                                                           3/1      6.5/1 6.5/1                                   Silicone oil and amount                                                       of TiCl.sub.4 g                                                               B.sub.2 O.sub.3                                                                             g                                                               Grinding time h        100      50    50                                      CHARACTERISTICS                                                               OF THE GROUND                                                                 PRODUCT                                                                       X-ray spectrum*                 A     A                                       TREATMENT                                                                     WITH TiCl.sub.4                                                               TiCl.sub.4    g        375      375   375                                     Ground product                                                                              g        25       25    25                                      Ground product                                                                of comp. Ex. 1                                                                              g                                                               Treatment temperature                                                                       ° C.                                                                            80       80    135                                     Filtration temperature                                                                      °C.                                                                             80       80    135                                     Washing with boiling                                                                        g                                                               heptane (amount)                                                              CHARACTERISTICS                                                               OF THE PRODUCT                                                                TREATED WITH                                                                  TiCl.sub.4                                                                    Elemental analysis: -Ti                                                                     % by     1.30     1.60  1.80                                                  weight                                                          Cl            % by     63.15    65.25 68.60                                                 weight                                                          Surface area  m.sup.2 /g        150   190                                     ______________________________________                                                    Measure                                                                              EXAMPLES                                                                 Units    4        5     Cfr. 1                                  ______________________________________                                        GRINDING                                                                      Vibrating mill volume                                                                       1        6        6     6                                       Rotary mill volume                                                                          1                                                               MgCl.sub.2    g        651.5    651.5 651.5                                   EB amount     g        158.5    158.5 158.5                                   MgCl.sub.2 /EB molar ratio                                                                           6.5/1    6.5/1 6.5/1                                   Silicone oil and amount                                                       of TiCl.sub.4 g                       200                                     B.sub.2 O.sub.3                                                                             g                                                               Grinding time h        100      100   100                                     CHARACTERISTICS                                                               OF THE GROUND                                                                 PRODUCT                                                                       X-ray spectrum*        B        B     B                                       TREATMENT                                                                     WITH TiCl.sub.4                                                               TiCl.sub.4    g        375      375                                           Ground product                                                                              g        25       25                                            Ground product                                                                of comp. Ex. 1                                                                              g                                                               Treatment temperature                                                                       °C.                                                                             80       130                                           Filtration temperature                                                                      °C.                                                                             80       135                                           Washing with boiling                                                                        g                                                               heptane (amount)                                                              CHARACTERISTICS                                                               OF THE PRODUCT                                                                TREATED WITH                                                                  TiCl.sub.4                                                                    Elemental analysis:                                                           Ti            % by     1.95     2.15  5.1                                                   weight                                                          Cl            % by     67.30    67.7  61.6                                                  weight                                                          Surface area  m.sup.2 /g                                                                             176      185   3                                       ______________________________________                                                    Measure                                                                              EXAMPLES                                                                 Units    6        Cfr. 2                                                                              7                                       ______________________________________                                        GRINDING                                                                      Vibrating mill volume                                                                       1                       1                                       Rotary mill volume                                                                          1                                                               MgCl.sub.2    g                       96.5                                    EB amount     g                       30.6                                    MgCl.sub.2 /EB molar ratio            5/1                                     Silicone oil and amount                                                                     g                       **PDMS                                  of TiCl.sub.4                         500/13.5                                B.sub.2 O.sub.3                                                                             g                                                               Grinding time h                       100                                     CHARACTERISTICS                                                               OF THE GROUND                                                                 PRODUCT                                                                       X-ray spectrum*                                                               TREATMENT                                                                     WITH TiCl.sub.4                                                               TiCl.sub.4    g        375            150                                     Ground product                                                                              g                       18                                      Ground product                                                                              g        25       25                                            of comp. Ex. 1                                                                Treatment temperature                                                                       °C.                                                                             80             80                                      Filtration temperature                                                                      °C.                                                                             80             80                                      Washing with boiling                                                                        g                 800                                           heptane (amount)                                                              CHARACTERISTICS                                                               OF THE PRODUCT                                                                TREATED WITH                                                                  TiCl.sub.4                                                                    Elemental analysis:                                                           Ti            % by     2.6      1.65  1.55                                                  weight                                                          Cl            % by              58.4                                                        weight                                                          Surface area  m.sup.2 /g        4                                             ______________________________________                                                    Measure                                                                              EXAMPLES                                                                 Units    8        9     10                                      ______________________________________                                        GRINDING                                                                      Vibrating mill volume                                                                       1        1        6                                             Rotary mill volume                                                                          1                       1                                       MgCl.sub.2    g        96.5     651.5 20                                      EB amount     g        30.6     157   6                                       MgCl.sub.2 /EB         5/1      6.5/1 5.2/1                                   molar ratio                                                                   Silicone oil and amount                                                                     g        **PDMS         **PDMS                                  of TiCl.sub.4          100/13.9       50/3                                    B.sub.2 O.sub.3                                                                             g                                                               Grinding time          100      100   100                                     CHARACTERISTICS                                                               OF THE GROUND                                                                 PRODUCT                                                                       X-ray spectrum*                                                               TREATMENT                                                                     WITH TiCl.sub.4                                                               TiCl.sub.4    g        375      375   150                                     Ground product                                                                              g        25       25    28                                      Ground product                                                                              g                                                               of Comp. Ex. 1                                                                Treatment     °C.                                                                             80       80    80                                      temperature                                                                   Filtration temperature                                                                      °C.                                                                             80       80    80                                      Washing with boiling                                                                        g                                                               heptane (amount)                                                              CHARACTERISTICS                                                               OF THE PRODUCT                                                                TREATED WITH                                                                  TiCl.sub.4                                                                    Elemental analysis:                                                           Ti            % by     1.65     2.00  1.1                                                   weight                                                          Cl            % by     62.05    62.55 66.1                                                  weight                                                          Surface area  m.sup.2 /g                                                                             172                                                    ______________________________________                                                    Measure                                                                              EXAMPLES                                                                 Units    11       --     --                                     ______________________________________                                        GRINDING                                                                      Vibrating mill volume                                                                       1        1                                                      Rotary mill volume                                                                          1                                                               MgCl.sub.2    g        45                                                     EB amount     g        10.1                                                   MgCl.sub.2 /EB molar ratio                                                                           6.8/1                                                  Silicone oil and amount                                                       of TiCl.sub.4 g                                                               B.sub.2 O.sub.3                                                                             g        54                                                     Grinding time h                                                               CHARACTERISTICS                                                               OF THE GROUND                                                                 PRODUCT                                                                       X-ray spectrum*                                                               TREATMENT                                                                     WITH TiCl.sub.4                                                               TiCl.sub.4    g        135                                                    Ground product                                                                              g        20                                                     Ground product                                                                of comp. Ex. 1                                                                              g                                                               Treatment temperature                                                                       °C.                                                                             80                                                     Filtration temperature                                                                      °C.                                                                             80                                                     Washing with boiling                                                          heptane (amount)                                                                            g                                                               CHARACTERISTICS                                                               OF THE PRODUCT                                                                TREATED WITH                                                                  TiCl.sub.4                                                                    Elemental analysis:                                                           Ti            % by     1.4                                                                  weight                                                          Cl            % by     3.1                                                                  weight                                                          Surface area  m.sup.2 /g                                                                             80                                                     ______________________________________                                         *Spectrum A is the spectrum in which the maximum intensity line of            magnesium chloride that appears at d = 2.56 A has decreased in relative       intensity and broadened asymmetrically forming a halo, the intensity peak     of which is comprised between d = 2.44 A and d = 2.97 A. Spectrum B is a      spectrum in which the aforesaid maximum intensity line is absent and          replaced by a halo having an intensity peak shifted with respect to such      line, and comprised between d = 2.44 A and d = 2.97 A.                        **PDSM 500, PDSM 100 and PDSM 50 are polydimethylsiloxanes having a           viscosity of 500, 100 and 50 centistokes, respectively.                  

                  TABLE 2                                                         ______________________________________                                        RESULTS OF THE PROPYLENE POLYMERIZATION                                                            REFERENCE                                                                     EXAMPLE IN                                                            Measure TABLE 1                                                                 Units     1       1     2                                      ______________________________________                                        CATALYST                                                                       COMPONENT                                                                    Catalyst component                                                            amount         mg        80      450   70                                     Ti             % by                                                                          weight    1.30          1.60                                   Cl             % by                                                                          weight    63.15         65.25                                  POLYMERIZATION                                                                RUNS                                                                          Autoclave capacity                                                                           l         2.5     30    2.5                                    Polymerization medium                                                                        cc        nC.sub.7.sup.+ /                                                                      C.sub.3.sup.- /                                                                     nC.sub.7.sup.+ /                       and volume               1000    23,000                                                                              1000                                   C.sub.3.sup.- effective pressure                                                             atm       5       26.5  5                                      Polymerization                                                                temperature    20° C.                                                                           60      65    60                                     Polymerization time                                                                          h         4       5     4                                      Type of Al-alkyl         TEA     TEA   TEA                                    Amount of Al-alkyl                                                                           g         1.135   12.5  1.135                                  Type of donor            PEA     PEA   PEA                                    Al alkyl/donor molar ratio                                                                             3.14    2.74  3.14                                   Hydrogen amount                                                                              Ncc       110     15000 110                                    RESULTS OF                                                                    POLYMERIZATION                                                                RUNS                                                                          Yield          g polymer/                                                                              113,500 274,000                                                                             103,000                                               g Ti                                                           Isotacticity index                                                                           %         94.0    94.5  93.5                                   CHARACTERISTICS                                                               OF THE POLYMER                                                                OBTAINED                                                                      Polymer apparent density                                                                     kg/l      0.47    0.45  0.44                                   Polymer intrinsic viscosity                                                                  dl/g      1.6     2.3   1.8                                    ______________________________________                                                             REFERENCE                                                                     EXAMPLE IN                                                            Measure TABLE 1                                                                 Units     3       4     4                                      ______________________________________                                        CATALYST                                                                      COMPONENT                                                                     Catalyst component                                                            amount         mg        127     66    310                                    Ti             % by                                                                          weight    1.80    1.95                                         Cl             % by                                                                          weight    68.0    67.30                                        POLYMERIZATION                                                                 RUNS                                                                         Autoclave capacity                                                                           l         2.5     2.5   30                                     Polymerization medium                                                                        cc        nC.sub.7.sup.+ /                                                                      nC.sub.7.sup.+ /                                                                    C.sub.3.sup.- /                        and volume               1000    1000  23,000                                 C.sub.3.sup.- effective pressure                                                             atm       5       5     26.5                                   Polymerization                                                                temperature    ° C.                                                                             60      60    65                                     Polymerization time                                                                          h         4       4     5                                      Type of Al-alkyl         TEA     TEA   TEA                                    Amount of Al-alkyl                                                                           g         1.135   1.135 12.5                                   Type of donor            PEA     PEA   PEA                                    Al alkyl/donor molar ratio                                                                             3.14    3.14  2.74                                   Hydrogen amount                                                                              Ncc       110     110   15,000                                 RESULTS OF                                                                    POLYMERIZATION                                                                RUNS                                                                          Yield          g polymer/                                                                    g Ti      107,000 155,000                                                                             324,000                                Isotacticity index                                                                           %         91.5    93.0  93.5                                   CHARACTERISTICS                                                               OF THE POLYMER                                                                OBTAINED                                                                      Polymer apparent density                                                                     kg/l      0.48    0.48  0.50                                   Polymer intrinsic viscosity                                                                  dl/g      2.0     1.8   2.1                                    ______________________________________                                                             REFERENCE                                                                     EXAMPLE IN                                                            Measure TABLE 1                                                                 Units     5       6     7                                      ______________________________________                                        CATALYST       COMPONENT                                                      Catalyst component                                                            amount         mg        82      72    110                                    Ti             % by                                                                          weight    2.15    2.15  1.55                                   Cl             % by                                                                          weight    67.7                                                 POLYMERIZATION                                                                RUNS                                                                          Autoclave capacity                                                                           l         2.5     2.5   2.5                                    Polymerization medium                                                                        cc        nC.sub.7.sup.+ /                                                                      nC.sub.7.sup.+ /                                                                    nC.sub.7.sup.+ /                       and volume               1000    1000  1000                                   C.sub.3.sup.- effective pressure                                                             atm       5       5     5                                      Polymerization                                                                temperature    ° C.                                                                             60      60    60                                     Polymerization time                                                                          h         4       4     4                                      Type of Al-alkyl         TEA     TEA   TEA                                    Amount of Al-alkyl                                                                           g         1.135   1.135 1.135                                  Type of donor            PEA     PEA   PEA                                    Al alkyl/donor molar ratio                                                                             3.14    3.14  3.14                                   Hydrogen amount                                                                              Ncc       110     110   110                                    RESULTS OF                                                                    POLYMERIZATION                                                                RUNS                                                                          Yield          g polymer/                                                                    g Ti      174,000 164,500                                                                             123,000                                Isotacticity Index                                                                           %         90.5    91.5  94.                                    CHARACTERISTICS                                                               OF                                                                            THE POLYMER                                                                   OBTAINED                                                                      Polymer apparent density                                                                     kg/l      0.43    0.48  0.49                                   Polymer intrinsic viscosity                                                                  dl/g      2.0     1.8                                          ______________________________________                                                             REFERENCE                                                                     EXAMPLE IN                                                            Measure TABLE 1                                                                 Units      8      9     10                                     ______________________________________                                        CATALYST                                                                      COMPONENT                                                                     Catalyst component                                                            amount         mg        63      65    110                                    Ti             % by                                                                          weight    1.65    2.00  1.1                                    Cl             % by                                                                          weight    62.05   65.00 66.1                                   POLYMERIZATION                                                                RUNS                                                                          Autoclave capacity                                                                           l         2.5     2.5   2.5                                    Polymerization medium                                                                        cc        C.sub.6 .sup.+ /                                                                      C.sub.6.sup.+ /                                                                     C.sub.7.sup.+ /                        and volume               1000    1000  1000                                   C.sub.3.sup.-  effective pressure                                                            atm       9       9     5                                      Polymerization                                                                temperature    ° C.                                                                             60      60    60                                     Polymerization time                                                                          h         4       4     4                                      Type of Al-alkyl         TIBAL   TIBAL TEA                                    Amount of Al-alkyl                                                                           g         1.97    1.97  1.135                                  Type of donor            EPT     EPT   PEA                                    Al alkyl/donor molar ratio                                                                             3.14    3.14  3.14                                   Hydrogen amount                                                                              Ncc       190     190   110                                    RESULTS OF                                                                    POLYMERIZATION                                                                RUNS                                                                          Yield          g polymer/                                                                    g Ti      353,000 344,000                                                                             141,000                                Isotacticity Index                                                                           % 92.0    92.5    92                                           CHARACTERISTICS                                                               OF THE POLYMER                                                                OBTAINED                                                                      Polymer apparent density                                                                     kg/l      0.50    0.43  0.48                                   Polymer intrinsic viscosity                                                                  dl/g      2.4     3.0   1.7                                    ______________________________________                                                             REFERENCE                                                                     EXAMPLE IN                                                            Measure TABLE 1                                                                 Units     11      cfr.1 cfr.2                                  ______________________________________                                        CATALYST                                                                      COMPONENT                                                                     Catalyst component                                                            amount         mg        100     105   105                                    Ti             % by                                                                          weight    1.3     5.7   1.65                                   Cl             % by                                                                          weight    31      61.0  58.4                                   POLYMERIZATION                                                                RUNS                                                                          Autoclave capacity                                                                           l         2.5     2.5   2.5                                    Polymerization medium                                                                        cc        C.sub.6.sup.+ /                                                                       C.sub.7.sup.+ /                                                                     C.sub.6.sup.+ /                        and volume               1000    1000  1000                                   C.sub.3.sup.- effective pressure                                                             atm       9       8     9                                      Polymerization ° C.                                                                             60      60    60                                     temperature                                                                   Polymerization time                                                                          h         4       5     4                                      Type of Al-alkyl         TIBA    TEA   TIBA                                   Amount of Al-alkyl                                                                           g         1.97    1.00  1.135                                  Type of donor            EPT     PEA   EPT                                    Al alkyl/donor molar ratio                                                                             3.14    2.9   3.14                                   Hydrogen amount                                                                              Ncc       190     1.70  190                                    RESULS OF                                                                     POLYMERIZATION                                                                RUNS                                                                          Yield          g polymer/                                                                    g Ti      290,000 70,000                                                                              89,500                                 Isotacticity index                                                                           %         90      90.5  88.5                                   CHARACTERISTICS                                                               OF THE POLYMERS                                                               OBTAINED                                                                      Polymer apparent density                                                                     kg/l      0.4     0.43  0.28                                   Polymer intrinsic viscosity                                                                  dl/g              1.9                                          ______________________________________                                    

EXAMPLE 12

Anhydrous MgCl₂ (containing less than 1% by weight of H₂ O) wasco-ground with the electron-donor compounds listed in Table 3, under theconditions used in Example 4. The ground product was treated with TiCl₄under the conditions of Example 4. The reaction product thus obtainedhad the Cl and Ti contents indicated in Table 3.

The catalyst components thus obtained were used to obtain finalcatalysts which were then used in polymerization runs under theconditions set forth in Example 8 with the only difference that theeffective C₃ pressure was 5.4 atm. The data concerning the yield ofpolymer and isotacticity index are reported in Table 3.

                  TABLE 3                                                         ______________________________________                                        Electron-donor                                                                             EPT     PEA     MB    MMA   NBE                                  ______________________________________                                        Ti % by weight                                                                             1.3     1.75    1.8   2.0   2.1                                  Cl % by weight                                                                             59.8    60.9    61    62    63.9                                 Yield (g polymer/                                                                          250,000 183,000 170,000                                                                             167,000                                                                             185,000                              g Ti)                                                                         Isotacticity index                                                                         92      93      94     94.5 92                                   ______________________________________                                         EPT = ethyl ptoluate                                                          PEA = p.ethylanisate                                                          MB = methylbenzoate                                                           MMA = methylmethacrylate                                                      NBE = di (n.butyl) ether                                                 

EXAMPLE 13

500 ml of kerosene were introduced into a flask provided with a stirrer.Propylene was introduced at a rate of 30 l/hr for 1 hour to expel airand moisture.

2.5 m mol of Al-triethyl and 0.884 mmol of the electron-donor compoundindicated in Table 4 were introduced into the flask at room temperature.Five minutes later a catalyst component prepared according to Example 7,with the only difference that a silicone oil having a viscosity of 20centistokes at 20° C. was introduced. The molar ratio Al/Ti in thecatalyst was 25.

The mixture was heated at 60° C. Propylene was polymerized for 1 hour atatmospheric pressure and was introduced at a rate to maintain thepressure constant during the polymerization. Thereafter, propylene wasreplaced by nitrogen and the reaction mixture was cooled to roomtemperature. The solid product was filtered off, washed twice withmethanol, then dried at 70° C. The soluble polymer was recovered byevaporation of the kerosene layer in the filtrate. The data concerningthe yield and the total isotacticity index of the polymer are reportedin Table 4.

                  TABLE 4                                                         ______________________________________                                        Electron-donor                                                                             BA      POBA    AAC   BAA   NBE                                  ______________________________________                                        Yield (g. polymer/g                                                                        47,900  43,140  40,430                                                                              41,900                                                                              31,500                                Ti)                                                                          Isotacticity index                                                                         75.6    89.2    80.3  73.9  92.1                                  (on the total)                                                               ______________________________________                                         BA = benzoic acid                                                             POBA = p.oxybenzoic acid                                                      AAC = alphaaminoacetic acid                                                   BAA = benzoic acid amide                                                      NBE = di (n.butyl) ether                                                 

EXAMPLE 14

10 g of a catalyst component prepared according to Example 13 andcontaining 2.1% by weight of Ti were suspended in 150 ml of kerosene.Diethylaluminum chloride (2.2 m. mol diluted with kerosene) was added atroom temperature and then 2.2 mmol of ethylbenzoate were added and themixture was stirred for 1 hour. The solid product was filtered, washedwith hexane, and dried in vacuum.

Into an autoclave of 2 l capacity and containing 750 ml of n.-hexane and3.75 mmol of Al(C₂ H₅)₃ premixed with 1.25 mmol of methyl p-toluate,there was introduced an amount of the dried product corresponding to0.03 mmol/l of Ti.

The polymerization run was carried out for 4 hours at 60° C. at apropylene pressure of 8 atm and in the presence of 400 N liter ofhydrogen.

After removal of the solid by filtration and drying, 225.9 g of powderwere obtained, the isotactic index of which was 94.2. From the filtrate5.9 g of polymer soluble in n-hexane were recovered.

EXAMPLE 15

10 g of MgCl₂ containing less than 1% by weight of water and suspendedin kerosene (100 ml) were treated with 18.4 ml of ethyl alcohol at 20°C. for 2 hours. The complex of MgCl₂ with ethanol was reacted with 2.5ml of 2,6-dimethylphenol at 20° C. for 1 hour, 11.7 ml of ethylbenzoateat 80° C. for 1 hour and 22.9 ml of Al(C₂ H₅)₂ Cl at 20° C. for 2 hours,in the order stated.

The solid product was separated by filtration, washed with n. hexane anddried in vacuum. 10 g of the product were treated with 100 ml of TiCl₄at 100° C. for 2 hours. The excess of TiCl₄ was separated by filtration.The solid product was washed repeatedly with n-hexane and then dried invacuum.

The elemental analysis of the product gave the following results:

Ti=3.60% by weight

Cl=58.0% by weight

31 mg of the solid product were used in a polymerization run under theconditions of Example 14. After removal of the solvent by filtration anddrying, 130 g of polymer were obtained. The isotactic index of thispolymer was 95.4. The polymer soluble in hexane and recovered from thefiltrate amounted to 30 g.

EXAMPLE 16 Catalyst Preparation

One (1) kg of anhydrous MgCl₂, 0.23 l of ethyl benzoate and 0.15 l ofPDMS* 50 were place in a 100 l vibrating mill (containing therein 350 kgof stainless steel balls, each 15 mm in diameter), in which they werebrought into mutual contact for 120 hr at 70° C.

Of the product of copulverization so obtained, 500 g was suspended in 5l of TiCl₄, and the resulting suspension was allowed to undergo reactionat 80° C. for 2 hr. After completion of the reaction, the resultingsystem was filtrated at the same temperature for recovery of its solidcomponent, which was then washed thoroughly with hexane until free TiCl₄was no longer detected.

The resulting solid component contained 2.0, 23.0 and 64.0 wt% of Ti, Mgand Cl as atoms and 10.5 wt% of ethyl benzoate respectively, andexhibited a specific surface area of 200 m² /g.

Polymerization

An equipment was used comprising 4 reactors lines up in series, namely,reactors A, B, D and E (each with an effective volume of 190, 120, 140and 200 l respectively) and a flash drum C (with an effective volume of30 l) installed between the reactors B and D.

The reactor A was charged with 0.75 mmol-Ti/hr as hexane slurry of thesolid CAT component prepared as described above, and a hexane solutionof triethyl-Al and ethyl p-toluate (EPT) in such amounts that the Al/Tiand Al/EPT mol ratios will be 50 and 2.75 respectively, all together ata rate of 21 l/hr as the total hexane quantity.

Furthermore, the reactor was charged with 7 Nm³ /hr of propylene and 13Nl/hr of hydrogen, while maintaining the reactor pressure at 7 kg/cm²Gauge and the polymerization temperature at 60° C. As the result, PP**having its isotacticity index and MI*** at 92.8% and 0.36 respectivelywas produced in the reactor A at a rate of 240,000 g-PP/g-Ti.

The polymer slurry discharged from the reactor A was then forwarded tothe reactor B, to which 4.5 mmol/hr of triethyl-Al and 5 Nl/hr of hexanewere charged anew. Polymerization in the reactor B was then performed ata 3.0 kg/cm² G pressure and 60° C. as the polymerization temperature.

PP having its isotacticity index at 92.2% and MI at 0.32 was produced inthe reactors A and B collectively at a rate of 290,000 g-PP/g-Ti.

The polymer slurry discharged from the reactor B was then directed tothe flash drum C, where unreacted propylene monomer was removed, andthereafter forwarded to the reactor D, to which 1,000 Nl/hr of ethyleneand 80 Nl/hr of hydrogen were supplied additionally, together withnitrogen gas to maintain the reactor pressure at 2.5 kg/cm² G.

The composition of the gas held in the reactor D was: hydrogen 7.3%,nitrogen 45.5%, ethylene 25.8%, propylene 0.9% and hexane 20.4%.

As the result of polymerization in the reactor D at 60° C. as thepolymerization temperature, a polymer having its MI at 0.29 and bulkdensity at 0.350 was obtained at a rate of 27,000 g-polymer/g-Ti.

The polymer slurry discharged from the reactor D was then forwarded tothe reactor E, to which ethylene was supplied at a rate of 1,700 Nl/hr,hydrogen at a rate of 70 Nl/hr, triethyl-Al 4.5 mmol/hr and hexane 10l/hr additionally.

Polymerization was carried out under the polymerization pressure of 2.0kg/cm² G and the polymerization temperature of 60° C., while thecomposition of the gas held in the reactor E was: hydrogen 38.2%,nitrogen 3.4%, ethylene 35.6%, propylene 0.1% and hexane 22.6%.

As the result of polymerization in reactor E, a polymer having its MI at0.24 and bulk density at 0.350 was produced at a rate of 24,000g-polymer/g-Ti. The polymer so produced contained 17.6 parts by weightof ethylene polymer per 100 parts by weight of PP.

In a further embodiment of the invention, the valence of tetravalent Ticontained in component (c) is reduced to a value lower than 4, bytreatment with reducing agents before component (c) is contacted withcomponent (a).

We claim:
 1. Catalysts for the polymerization of alpha-olefinscontaining at least 3 carbon atoms and mixtures thereof with ethylene,comprising the product obtained by contacting the following startingcomponents:(a) a hydrocarbyl Al compound not containing halogen atomsdirectly bound to Al; (b) a hydrocarbyl electron-donor capable offorming complexes or substitution reaction products with the Al compound(a) in such amount that 15% to 100% of the Al compound is combined withthe electron-donor compound; and (c) a solid component comprising, atleast on the surface, the reaction product of a Mg dihalide with ahalogenated teatrvalent Ti compound selected from the group consistingof Ti tetrahalides and Ti halogen alcoholates and with a hydrocarbylelectron-donor capable of forming complexes with Mg dihalides, the molarratio electron-donor/Ti in said product being higher than 0.2 and themolar ratio halogen atoms/Ti being comprised between 10 and 90,component (c) being further characterized in that at least 80% by weightof the tetravalent Ti compounds contained therein is insoluble inboiling n-heptane and in that at least 50% by weight of the Ti compoundsinsoluble in n-heptane is insoluble in TiCl₄ at 80° C., and also in thatthe surface area of the product insoluble in TiCl₄ at 80° C., and thesurface area of component (c) as such, is higher than 40 m² /g.
 2. Thecatalysts of claim 1 in which component (c) is further characterized inthat the X-rays spectrum thereof shows a halo the maximum intensity ofwhich is shifted with respect to the distance d of the maximum intensityline which appears in the X-rays spectrum of the corresponding normal Mgdihalide.
 3. Catalysts according to claim 1, in which the electron-donorcompound is an ester of an organic carboxylic acid.
 4. Catalystsaccording to claim 1, in which the electron-donor compound is an esterof an aromatic carboxylic acid.
 5. Catalysts according to claim 1, inwhich the amount of electron-donor compound (b) is from 0.2 to 0.4 molesper mole of the organometallic Al compound, component (a).
 6. Catalystsaccording to claim 1, in which, in component (c), the Mg/Ti molar ratiois comprised between 10 and 30; the halogen/Ti atomic ratio is comprisedbetween 20 and 80; and the electron-donor compound/Ti molar ratio iscomprised between 1.2 and
 3. 7. Catalysts according to claim 1, in whichcomponent (c) is characterized in that the surface area of the productinsoluble in Ti tetrachloride at 80° C., and the surface area ofcomponent (c) as such, is greater than 100 m² /g.
 8. Catalysts accordingto claim 7, in which component (c) is characterized in that the surfacearea of the product insoluble in Ti tetrachloride at 80° C., and thesurface area of component (c) as such, is comprised between 100 and 200m² /g.
 9. Catalysts according to claim 1, in which component (c)contains inert solid fillers other than Ti oxides and Ti salts ofoxygen-containing inorganic acids, in amounts up to 80% by weight basedon the total weight of the component.
 10. Catalysts according to claim1, in which component (c) is deposited on SiO₂ or Al₂ O₃ having aporosity higher than 0.3 cc/g.
 11. Catalysts according to claim 1, inwhich component (c) contains inert fillers selected from the groupconsisting of TiO₂ and Ti salts of inorganic oxygen-containing acids,and in which the Mg/Ti ratio is lower than
 1. 12. Catalyst according toclaim 1 in which component (c) is mixed with an agglomerating substanceselected from the group consisting of B₂ O₃ and AlCl₃.
 13. Catalystsaccording to claim 12, in which the surface area of the mixed product issmaller than 40 m² /g.
 14. Catalysts according to claim 1, in whichcomponent (c) is prepared by reacting a liquid halogenated tetravalentTi compound with a solid composition comprising a Mg halide selectedfrom the group consisting of Mg dichloride and Mg dibromide, and acomplex between the Mg dihalide and the electron-donor compounds inwhich composition the ratio Mg/moles of electron-donor is higher than 2,said solid composition being characterized in that in its X-raysspectrum the maximum intensity line appearing in the X-rays spectrum ofthe corresponding normal Mg dihalide, as defined in ASTM 3-0854 and15-836 for the Mg dichloride and Mg dibromide respectively, is decreasedin relative intensity and asymmetrically broadened to form a halo thatshows an intensity peak shifted with respect to interplanar distance dof the maximum intensity line, or the spectrum is characterized in thatthe maximum intensity line is absent and in its place there appears ahalo having an intensity peak shifted with respect to distance d of themaximum intensity line.
 15. Catalysts according to claim 14, in whichthe Mg/moles of electron-donor molar ratio is between 2 and
 15. 16.Catalysts according to claim 15, in which the electron-donor is selectedfrom the group consisting of organic ethers and esters of organiccarboxylic acids.
 17. Catalysts according to claim 15, in which theelectron-donor is an ether or ester of an aromatic carboxylic acid. 18.Catalysts according to claim 15, in which the electron-donor is analiphatic ether.
 19. Catalysts according to claim 14, in which component(c) is prepared by reacting the liquid halogenated tetravalent Ticompound with Mg dichloride and the intensity peak appearing in theX-rays spectrum of the component is comprised in the range from d 244 Ato d 2.97 A.
 20. Catalysts according to claim 14, in which the Ticompound is reacted with a product obtained by grinding mixtures of Mgdichloride or Mg dibromide with the electron-donor compound. 21.Catalysts according to claim 20, in which the electron-donor compoundcoground with the Mg dichloride or Mg dibromide is an aliphatic oraromatic ether.
 22. Catalysts according to claim 1, in which the mixturewhich is ground includes at least one grinding promoter selected fromthe group consisting of silicone oils and inert solid substances. 23.Catalysts according to claim 14, in which the reaction with the liquidTi compound is conducted at a temperature ranging from 20° C. to 200°C., and the solid reaction product is separated from the liquid phaseunder conditions such that less than 50% of Ti compounds extractablewith TiCl₄ at 80° C. remains on the solid product.
 24. The catalysts ofclaim 1, in which the valence of tetravalent Ti contained in component(c) is reduced to a value lower than 4 by treatment with reducing agentsbefore component (c) is contacted with component (a).
 25. A solidcomponent for catalysts for polymerizing alpha-olefins, comprising atleast on the surface, the reaction product of a Mg dihalide with ahalogenated tetravalent Ti compound selected from the group consistingof Ti tetrahalides and Ti halogen alcoholates and with a hydrocarbylelectron-donor capable of forming complexes with Mg dihalides, the molarratio electron-donor/Ti in said product being higher than 0.2 and themolar ratio halogen atoms/Ti being comprised between 10 and 90, saidcomponent being further characterized in that at least 80% by weight ofthe tetravalent Ti compounds contained therein is insoluble in boilingn-heptane and in that at least 50% by weight of the Ti compoundsinsoluble in n-heptane is insoluble in TiCl₄ at 80° C., and also in thatthe surface area of the product insoluble in TiCl₄ at 80° C., and thesurface area of said component as such, is higher than 40 m² /g.
 26. Asolid component for catalysts for polymerizing alpha-olefins accordingto claim 25, which component has been treated with a reducing agent inorder to reduce the valence of Ti contained therein to a value lowerthan
 4. 27. A solid component for catalysts for polymerizingalpha-olefins according to claim 25 in which the Mg dihalide is obtainedby reaction of a Ti tetrahalide with an oxygen-containing Mg compound.28. A solid component for catalysts for polymerizing alpha-olefinsaccording to claim 27 in which the oxygen-containing Mg compound isselected from the group consisting of MgO, Mg(OH)₂, Mg(OH)Cl, Mgcarbonate, Mg salts of organic acids, Mg silicate, Mg aluminates, Mgalcoholates and halogenated derivatives thereof.
 29. A solid componentfor catalysts for polymerizing alpha-olefins according to claim 25, inwhich the Mg dihalide is obtained by reaction of Ti tetrahalide with ahydrated Mg dihalide containing from 0.1 to 6 moles of H₂ O per mole ofdihalide.